Variable-frequency drive

A variable-frequency drive (VFD) is a device used to control the speed and torque of an AC motor by changing the motor input frequency and voltage.

Applications

VFDs are used for many things that range from small appliances to large mining motors and compressors.

Variable-frequency Drive Media

Chassis of above VFD (cover removed)
Excerpted from a copyrighted Powerpoint presentation and donated by the author
Voltage-source inverter topology
Current-source inverter topology
Six-step drive waveforms per voltage-source inverter phase leg.
Topology of direct matrix converter
Line regenerative variable-frequency drives, showing capacitors (top cylinders) and inductors attached, which filter the regenerated power

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